A secondary battery quick-charging circuit is disclosed in Japanese Utility Model Application No. 134231/1979. According to this application, a silicon controlled rectifier is controlled by the charging current of a capacitor. This arrangement is disadvantageous because in the event the supply voltage varies after the battery has been fully charged and during a period when overcharge is being prevented, a charging current flows in the capacitor and the silicon controlled rectifier is erroneously operated.
Japanese Utility Model Application No. 36745/1982 discloses a secondary battery quick-charging circuit wherein after the battery has been fully charged, a small current continues to flow in a transistor. The disadvantage of this arrangement is the resultant loss of electric power irrespective of the battery charging operation.